The present invention comprises a new and distinct hybrid Rhododendron cultivar hereinafter referred to by the cultivar name ‘NCRX1’. Developed by a breeding program in Mills River, N.C., ‘NCRX1’ was selected for its growth and survival in full sun and clay loam soils as well as its ornamental characteristics. ‘NCRX1’ was obtained from a population of seedlings derived from a controlled cross of the seed parent Rhododendron ‘Pride's Early Red’ (unknown parentage, unpatented) x the pollen parent Rhododendron hyperythrum 2006-029 (unpatented) in 2007. Rhododendron ‘Pride's Early Red’ was used as a parent because of its cold hardiness (USDA Zone 5) and dark red flower color. Rhododendron hyperythrum, a species native to Taiwan, was used as a parent because of its heat tolerance and resistance to Phytophthora root rot (Arisumi et al., 1986; Hoitink and Schmitthenner, 1975).
The first asexual propagation of ‘NCRX1’ occured in July 2010 by rooting stem cuttings at a research nursery in Mills River, N.C. ‘NCRX1’ roots readily from firm softwood cuttings treated with a basal dip of 5,000 ppm indole butyric acid (potassium salt) in water. ‘NCRX1’ has been found to retain its distinctive characteristics through successive asexual propagations over the course of 8 years. At least three generations have been reproduced and have shown that the unique features of this cultivar are stable and reproduced true to type.